Patterns of morphological variation among fossorial, piscivorous, and durophagic snakes reveal several principles underlying character co-occurrence. Homoplasy is widespread among all three groups. Alternative adaptive responses to specialized habits include modifications for cranial reinforcement in fossorial and cryptozoic snakes and columellar adjustments to accommodate large excursion of the quadrates in piscivores.Among durophagic species alternatives include dental attachment in both scincivores and crustacean-eaters. Although it may be difficult to distinguish primary adaptive responses from secondary ones, specialization frequently elicits pervasive modifications across manymorphological systems. Some are associated with the foraging microhabitat, such as valvularity in piscivores and arboreal adaptations in cochleophages. Others, such as mimicry in Dasypeltis and Scaphiodontophis, are defensive. Still others reflect special aspects of prey processing, such as hypertrophy of the gastric smooth muscle and presumptive salt glandin Fordoma, a cancrivore. The extent to which coordinated morphological responses necessarily accompany specialization is important in formulating hypotheses of macroevolutionary mechanisms.